Từ nguyên

From earlier goodby, Godby, Godby'e, Godbwye, God b'w'y, God bwy yee, God buy you, God be wi' you, each a progressively shorter contraction of "God be with ye" or "God be with you". Note the change of God to good by confusion with good morning, good night, etc. Modernly analysed as good + bye.